Cardiac Rehabilitation - Literature review Example

Background & introduction Cardiac patients have benefited from cardiac rehabilitation (CR) which has been hailed to reduce death incidences by over 20% in the past two decades (Oldridge, 1988). Objective outcomes were needed for exact evaluation of the values entailed in the relationship. Many studies have employed cardio-respiratory fitness (CRF) for such evaluations. A specific outcome measure that can be employed to measure CRF is the VO2max (ml·kg-1·min-1). This is a representation of the maximum oxygen consumed by an individual. The amount of oxygen consumed is directly related to the energy consumed by an individual. The energy consumed by an individual is dependent on various factors such as age, co-morbidities (Morris et al., 1993), the fitness level of an individual (Jetté et al., 1990) and body mass (Byrne et al., 2005). The energy consumed is expressed as metabolic equivalents (METs) and a single METs is approximately equal to 3.5 (ml·kg-1·min-1). Dorn et al. (1999) established that deaths related to cardiac disorders can be reduced by cardio-respiratory fitness improvement. In his study, Vanhees et al. (1994) found out that there was a 2% decline in deaths related to cardiovascular disorders when VO2peak was increased by 1%. Moreover, Dorn et al. (1999) established that exercise capacity increase by 1 MET resulted in 10% decline of cardiovascular mortality risk. However, this study was limited by the fact that it did not provide information on the impact of the program on quality of life and hospitalization. Similar results were obtained by Kavanagh et al. (2003) who reported a 10% decrease in mortality for each MET. It is thus apparent that CRF increment is a vital outcome in cardiovascular rehabilitation programs. A treadmill Meta-analysis carried out by Myers et al., (2009) established that patients undertaking cardiac rehabilitation improved their cardio-respiratory fitness. The analysis involved 24 studies that involved 2115 subjects. The authors reported that there was a significant increase in cardio-respiratory fitness following a CR program. They reported that patients undertaking 48 and above exercise sessions recorded a 0.78 METs mean improvement. Contrary to this finding, many clinics are reported to use an average of 16 exercise sessions in USA (Brodie et al., 2006). In addition, most clinics prefer using simple, cheap and practical assessments like ISWT instead of gold standards assessments such as cycle eargometer and treadmill. Gold standard assessments are characterised by being complex, time consuming and more expensive. Majority of cardiac patients are overage and are not used to treadmill cycling or walking. In addition, the requirement of using mask and nose clip for gas analysis is often uncomfortable for cardiac patients during exercise (Page et al., 1994). Other exercises like walking are more simple, cheap and practical. Cardio-respiratory fitness measurement in the USA is mainly based on ISWT (Brodie et al., 2006). In spite elaborate documentation of cardiac rehabilitation benefits O’conner, (1989); the frequency and duration of optimal CR program is not well-documented (Hevey et al., 2003). Arnold et al., (2007) used ISWT to compare patients undergoing supervised CR twice a week and once a week for six weeks. They established that there was no significant variation in the distances walked between the two groups during the whole rehabilitation period. The reliability of these findings however raises some issues. A close analysis of the baseline data provided for shuttle walking distances indicated that there were some significant variations between the two groups. This variation was not accounted for by statistical data analysis. To legitimise there results, Arnold et al (2007) argues that their study was only concerned with the impact of CR session frequency. It is clear however that the kind of exercise undertaken during one of the more frequent session differed from that undertaken by both groups during proceeding sessions. Thus, the kind of exercise is another variable. Thus, the validity of the results is lowered due to reduction in session standardization. The standardization of the sessions is further lowered by the fact that patients were advised to undertake more exercise sessions while at home. This contradicted the aim of the study, which was to compare the impact of two frequencies on supervised rehabilitation. However, the authors controlled this by encouraging patients to record such additional exercise sessions in their diaries. In spite this; data analysis does not indicate whether such additional exercises were controlled and hence indicating that diary record was not considered. Functional capacity of all patients involved in the six-week CR program improved significantly. However, the investigation was unable to establish a clear optimum frequency for CR since the findings showed similar level of improvements between the two groups. The 2002 Scottish Intercollegiate Guidelines Network (SIGN) are the most specific guidelines in the USA. The guideline recommend that phase III CR be administered twice a week for at least eight weeks. The SIGN guidelines recommendations are the only ones, which are based on research findings. This is contrary to the 2007 National Institute of Clinical Excellence (NICE) guidelines, which do not recommend CR sessions optimum frequency. Emphasis is placed on the benefits of attaining individual needs in national guidelines like NSF (2000). These guidelines argue that these benefits can be attained in different ways. In spite NSF quoting typical service provision and recommending that at least two supervised sessions be undertaken twice a week: it does not provide supporting evidence. The guideline also acknowledges that self-help manuals are beneficial and that there is no requirement for formal supervision. The SIGN (2002) provides grade A evidence for a minimum of two sessions per week for at least eight weeks and grade C evidence for a single session per week group exercise and two home sessions for cardiac rehabilitations. These exercises are argued to be more effective than three sessions per week in hospital environment. This study aims at establishing whether functional capacity is significantly increased by CR when carried out twice a week or whether it remains effective when carried out once a week. This study will help to provide additional evidence to assist in the improvement of CR program delivery and to help in gaining additional funding. Moreover, the study will also help in ascertaining to whether the increased costs incurred for higher frequency CR program are justified. The study will adopt a straightforward methodology and a single independent variable in order to avoid the shortcomings that plagued previous similar studies. Confounding variables and baseline characteristics differences will be controlled. The CR sessions were based on that advocated for by the American Association of Cardiac Rehabilitation for the purposes of session standardization. Methods Sample Population Forty-nine patients were involved in a retrospective analysis. The patients had undergone supervised, rigorous phase II CR program in two CR centres based in Brisbane. During the program, patients took part in training exercises, educational talks and relaxation sessions. The final 49 patients included in the analysis were arrived at after 5 patients were excluded from the study. Twenty-nine patients participated in a two session per week while 20 underwent one session per week of CR. The subjects were of either gender and had cardiac disorders. Clinically unstable patients were excluded from rehabilitation program while those who were unable to finish final shuttle walk after rehabilitation program were excluded from the study. Patients were recruited from selected rehabilitation centres based in Brisbane and the centres had similar standardized conditions. The CR was thorough and thus it enabled patients to exercise and to attend educational sessions. The study was undertaken for 12-week duration. Outline of Rehabilitation Patients undertook a 15 minute warm up exercise each time the visited the clinic. This enabled them to increase their metabolic demand, warm up their main muscle groups and to mobilize their joints. During this time, the subjects exercised on the 6-20-point Borg scale at an intensity of between 6 and 7 (BACR guidelines, 2005). The patients participated in alternating exercise circuit in aerobic and resistance stations during the core exercise session. At this time, the subjects exercised on the 6-20-point Borg scale at an intensity of between 7 and 8 at 90% of their maximum heart rate predicted. The whole session lasted for thirty minutes (SIGN, 2002). This session was followed by a 10-minute cool down. The patients finally underwent a five-minute relaxation session based on SIGN (2002) recommendations. The patients’ heart rate and pressures were recorded prior and after every clinic. Outcome Measure ISWT was the primary outcome measure during this investigation. This is based on Arnott (1997) argument that ISWT provides a reproducible measure of the functional capacity of CR patients. The patients were required to walk a nine metres distance between 2 cones, which had an audio signal. The patients were required to move to the next difficult level following each minute of the test. A triple beep was used to signal the next level. The speed of walking was increased by 0.7 miles per hour for a 12-minute period. The patients' resting blood pressure, heart rates were recorded prior, and 5 minutes following each shuttle walk test. The Rates of Perceived Exertion (RPE) and heart rates of patients were recorded during shuttle walks (SIGN, 2002). The test was stopped by any of the following factors: inability of the patient to meet the required speed, the patient experiencing dizziness or chest pains or any other contra-indicative signs, the attainment of >=85% of the predicted heart rate, attaining >15 perceived level of exertion on the 6-20 point Borg scale or finishing the 12 minute test (SIGN, 2002). Data Analysis Statistical analysis was carried out using the Statistical Package for Social Sciences (SPSS) Version 18.0 (SPSS Inc., Chicago, IL. USA). A p-value Read More